Changeling;
You might want to look here - lots of PRESSURE TESTED heavy load data:
http://www.customsixguns.com/writing...g_the_myth.htm
Typically, you can load a 260 gr Keith or LBT WFN or WLN from 650 fps - 1200/1300 fps within safe limits for the .45 Colt Blackhawk using John Linebaughs pressure tested data.
My self, I'll be staying within 25,000 psi in my Ruger Bisley SS .45 Colt/.45 ACP convertible.
Factory load levels with the Lyman 452664 or NOE's Lyman 454424 Clone will receive most of my attention. That level makes a really good general load level and is pleasant to shoot.
FWIW
Dale53